Waveform quality feedback for the selection of gateways

ABSTRACT

Techniques are disclosed for selecting transmission resources in a telecommunications system that comprises different networks, where the techniques are based on the quality of the waveform of transmitted media such as audio or video signals, in contrast to the quality of service of the network that transports the media. The problem with only using quality of service to determine which resources to allocate to a call is that quality of service does not guarantee that the quality experienced by the call&#39;s participants is satisfactory just because a component network&#39;s quality of service is satisfactory. For example, the end-to-end delay experienced in a VoIP network might be satisfactory for most data transfers, but might still be inadequate to control the echo experienced by telecommunications users. The disclosed techniques evaluate the waveform quality (i.e., in terms of loudness, noise, echo, and so forth) of media that is transmitted along a path and allocate alternative resources accordingly.

FIELD OF THE INVENTION

The present invention relates to telecommunications in general and, moreparticularly, to using, for feedback purposes, the waveform quality ofmedia that is transmitted along a path.

BACKGROUND OF THE INVENTION

FIG. 1 depicts a schematic diagram of telecommunications system 100 inthe prior art. System 100 comprises telephones 101 and 109, PublicSwitched Telephone Networks (PSTN) subnetworks 102 and 108, InternetProtocol (IP) gateways 103 and 107, Internet Protocol network 104, andInternet Protocol endpoints 105 and 106, interconnected as shown. System100 enables telephones 101 and 109 and endpoints 105 and 106, as well asother telecommunications terminals, to communicate with each othervarious kinds of media such as audio, video, and so forth.

Each of telephones 101 and 109 is a telecommunications terminal that iscapable of making calls to or receiving calls from any othertelecommunications terminal—PSTN-based or IP-based—in telecommunicationssystem 100.

Public Switched Telephone Network subnetworks 102 and 108 are portionsof the Public Switched Telephone Network (PSTN). Subnetwork 102comprises access paths, switches, and transmission paths, in acombination of analog and digital technology, which enable telephone 101to communicate with other terminals. Subnetwork 108 also comprisesaccess paths, switches, and transmission paths, in a combination ofanalog and digital technology, which enable telephone 109 to communicatewith other terminals. Each depicted portion of the PSTN might comprisewireline equipment, wireless equipment, or both wireline and wirelessequipment.

Internet Protocol gateways 103 and 107 are nodes that act as accesspoints into Internet Protocol network 104 for signals from PSTNsubnetworks 102 and 108, respectively.

Each of Internet Protocol endpoints 105 and 106 is a packet-capabletelecommunications terminal that communicates via the Internet Protocol.Each endpoint is capable of making calls to or receiving calls from anyother telecommunications terminal—PSTN-based or IP-based—intelecommunications system 100.

Internet Protocol network 104 is a packet-switched network that iscapable of transporting packets from one node to another. Thetransported packets can comprise voice or video signal information intheir payloads and can also comprise Real-time Transport Protocol (RTP)headers, User Datagram Protocol (UDP) headers, or IP headers. When thepackets comprise voice signal information with IP headers, they areoften referred to as Voice over Internet Protocol (VoIP) packets, andthe networks that transport the VoIP packets are often referred to asVoIP networks. When each node in network 104 can be both a sender ofpackets and a receiver, there are k*(k−1) network paths through network104, wherein k is positive integer that represents the number of nodesin the network.

The service provided by a network path in network 104 can becharacterized by its “quality of service,” which, for the purposes ofthis specification, is defined as a function of the bandwidth, errorrate, and latency from one node to another. For the purposes of thisspecification, the “bandwidth” from one node to another is defined as anindication of the amount of information per unit time that can betransported from the first node to the second. Typically, bandwidth ismeasured in bits or bytes per second. The bandwidth exhibited by thenetwork can be compared to the bandwidth requirements of one or moremedia flows; the “bandwidth requirement” is the amount of informationper unit time per media flow that has to be transported from the firstnode to the second, usually determined by the signal encoding protocol(e.g., G.711 for voice, etc.) that governs the particular media flow.For the purposes of this specification, the “error rate” from one nodeto another is defined as an indication of the amount of information thatis corrupted as it travels from the first node to the second. Typically,error rate is measured in bit errors per number of bits transmitted orin packets lost per number of packets transmitted. For the purposes ofthis specification, the “latency” from one node to another is defined asan indication of how much time is required to transport information fromone node to another, plus any packetization delays and buffering delaysthat accumulate at the endpoints. Typically, latency is measured inmilliseconds. The quality of service provided by network 104 can varybased on the actual bandwidth, error rate, and latency experienced bythe call or session that is being carried by network 104, in relation tothe requirements for the bandwidth, error rate, and latency for the callor session.

The quality experienced in telecommunications system 100 can also dependon other factors. First, each of telephones 101 and 109 can influenceaudio call clarity through the quality of its loudspeaker andmicrophone, the loudness of the transmitted and received signal, and theacoustic echo generated between the loudspeaker and microphone. Second,where each of PSTN subnetworks 102 and 108 converts the analog voicesignals from a telephone into digital signals to yield greaterefficiency in the transmission backbone, digitizing those voice signalscan affect the clarity. Third, each of gateways 103 and 107 can affectthe clarity through its components such as speech codecs, silencesuppression mechanisms, comfort noise generators, jitter buffers, andecho cancellers. And fourth, each of endpoints 105 and 106 also canaffect the clarity through its components such as a speech codec, asilence suppression mechanism, and the quality of its loudspeaker andmicrophone. Many of the impairments that are presently experienced bytelecommunications users are as the result of different networks, suchas Voice over Internet Protocol networks versus the PSTN, having tointeroperate with each other, where some of those networks—or at leastthe commercial application of those networks—are relatively new intelecommunications. Both the differences between the networks and theequipment that is necessary to enable the different networks tointeroperate, such as gateways, are some of the causes of impairments,many of which were either imperceptible or nonexistent in a PSTN-onlytelecommunications environment.

Other configurations of “hybrid” telecommunications systems thatcomprise both PSTN and IP-based networks also exist in the prior art. Inthose other systems, as in the telecommunications system described aboveand with respect to FIG. 1, both the PSTN and the gateways that bridgethe PSTN and IP-based networks can be sources of impairments.

SUMMARY OF THE INVENTION

The present invention is a technique for selecting transmissionresources in a telecommunications system that comprises multiple,different networks, where the technique is based on the quality of thewaveform of transmitted media such as audio or video signals, incontrast to the quality of service (i.e., the bandwidth, error rate, orlatency) of the network that transports the media. The problem with onlyusing quality of service to determine which resources to allocate to acall is that quality of service does not guarantee that the qualityexperienced by the call's participants is satisfactory just because acomponent network's quality of service is satisfactory. For example, ina Voice over Internet Protocol (VoIP) network that is part of thebroader, hybrid telecommunications system, the quality of service-basedmetric of end-to-end delay might be satisfactory for most datatransfers, but might still be inadequate for controlling the echo thatis experienced by end users across the overall telecommunicationssystem. The present invention recognizes the limitations of only usingquality of service and attempts to provide an improvement in the qualityperceived by users, without some of the costs and disadvantages fordoing so in the prior art.

The techniques of the illustrative embodiments attempt to provide animprovement in the quality as evaluated at the waveform level—ratherthan merely at the packet level as is done to determine quality ofservice—for media that is transmitted along a path. Waveform quality isevaluated in terms of one or more of loudness, distortion, noise,fading, crosstalk, echo, and so forth. The techniques seek to improvethe waveform quality of media that is transmitted along a path (i) byperiodically or sporadically evaluating alternative routes and (ii) bysending one or more packets through evaluated routes that will resultin, or are believed will result in, an acceptable waveform quality forthe call or session. Some embodiments of the present invention areparticularly well-suited for applications that are sensitive to waveformquality issues, such as the provisioning of telephony and streamingaudio and video over multiple, different networks, including InternetProtocol networks (e.g., VoIP networks, etc.) that have to co-exist andinteroperate with the Public Switched Telephone Network, as part of ahybrid telecommunications system.

In accordance with the first of two illustrative embodiments of thepresent invention, the sending node at the edge of an Internet Protocolnetwork—or some agent acting on behalf of the sending node—exercises thecapability to either:

-   -   i. transmit a packet “directly,” in which case the packet will        traverse the network on a “nominal” path in well-known fashion,        or    -   ii. transmit the packet “indirectly,” in which case the packet        will be sent to a relay node, which forwards the packet to the        receiving node on the other end of the IP network, which        receiving node then forwards the media signals represented in        the packet to the destination node of the call or session.        When the sending node or agent has the option of sending the        packet either (i) directly or (ii) through one or more indirect        paths, the sending node or agent can evaluate the waveform        quality that is associated with multiple paths between the        sending node and the receiving node, and can then intentionally        choose a path for the packet that is advantageous. In some        embodiments, the sending node or agent also has the option of        sending the packet through an alternative network, such as one        that has been conditioned to provide optimum waveform quality.        The result is that by giving the sending node more than one        option for routing the packet, the likelihood is increased that        the sending node can route the packet through a network path        with a satisfactory waveform quality as perceived by the        participants in a call or session.

In accordance with the second of two illustrative embodiments of thepresent invention, an Internet Protocol (IP) source node at the edge ofa telecommunications system—or some agent acting on behalf of the sourcenode—exercises the capability to transmit a packet to any one ofmultiple gateways that bridge the local IP network to the PublicSwitched Telephone Network (PSTN) in the telecommunications system.Similarly, a gateway at the edge of the PSTN in the telecommunicationssystem exercises the capability to connect to any other gateway at theedge of the PSTN. When a source node or agent has the option of sendinga packet to one of multiple gateways, or a gateway has the option ofconnecting to one of multiple gateways across the PSTN, or both, thesource node or agent can evaluate the waveform quality that isassociated with the multiple paths between the source node anddestination node, and can then intentionally choose an advantageouscommunication path for the packet. These options can reduce impairmentsin a telecommunications system where a gateway or PSTN communicationpath is a source of impairments, by selecting another gateway orcommunication path with better performance, as measured by the waveformquality. The result is that by providing the source node with more thanone path to the destination node, the likelihood is increased that thesource node can route the packet through a communication path with asatisfactory waveform quality as perceived by the participants in a callor session. The claims in the present application comprise aspects ofthe techniques that are embodied in this second illustrative embodiment.

The techniques of the illustrative embodiments select the utilized pathin response to evaluating the waveform quality of the transmittedsignals. However, it will be clear to those skilled in the art, afterreading this specification, how to affect other call-related resourcesor functions in response to the evaluated waveform quality, such asmuting or unmuting the media signal paths of a conference call byselectively disabling or re-enabling, respectively, the flow of packets.Furthermore, the techniques of the illustrative embodiments are in thecontext of a telecommunications system that comprises an InternetProtocol-based network. However, it will be clear to those skilled inthe art, after reading this specification, how to apply the techniquesto where other types of networks are present, such as networks that areasynchronous transfer mode (ATM) based or frame relay based, or based onsome combination thereof.

It will also be clear to those skilled in the art that the indirectpacket transmission method can use multiple relay nodes and, therefore,multiple indirections to transmit packets from the sending to receivingnode. A collection of relay nodes can be logically interconnected insome topology, arbitrary or otherwise, and can use rules or policies, orboth, for selecting logical interconnections. The resulting logicalnetwork is often referred to as an “overlay network” or“application-level network.” Embodiments of the present inventionencompass the use of one or more overlay networks for packettransmission, added to a preexisting packet-switched network, usingnetwork-level switching protocols (e.g., Ethernet, etc.) orinternetwork-level routing protocols (e.g., Internet Protocol, etc.), orsome combination thereof.

It will also be clear to those skilled in the art that the techniqueused in the first illustrative embodiment to respond to the waveformquality evaluations can be applied to the IP-based networks of thesecond illustrative embodiment, and conversely that the technique usedin the second illustrative embodiment to respond to waveform qualityevaluations can be applied to the PSTN subnetworks and gateways of thefirst illustrative embodiment.

An illustrative embodiment of the present invention comprises evaluatingthe waveform quality of media that is transmitted along a firstcommunication path from a first node to a second node, wherein the firstcommunication path traverses: (i) a first network that ispacket-switched, (ii) a first gateway that is contiguous with the firstnetwork, and (iii) a second gateway that is non-contiguous with thefirst network; and when the waveform quality is unsatisfactory,transmitting a first packet along a second communication path from thefirst node to the second node, wherein the second communication pathtraverses the first network and at least one of: (i) a third gatewaythat is contiguous with the first network, and (ii) a fourth gatewaythat is non-contiguous with the first network; wherein the firstcommunication path fails to provide a quality-of-service guarantee.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic diagram of telecommunications system 100 inthe prior art.

FIG. 2 depicts a schematic diagram of telecommunications system 200 inaccordance with the first illustrative embodiment of the presentinvention.

FIG. 3 depicts a schematic diagram of the salient components ofsubsystem 210, which is part of system 200.

FIG. 4 depicts the primary nominal path through network 204 from sendingendpoint 205 to receiving gateway 207, which elements compose subsystem210 and which primary nominal path comprises nodes 11, 15, 20, 24, 29,25, 22, and 26.

FIG. 5 depicts the primary nominal path and all of the alternativenominal paths through network 204 from sending endpoint 205 to receivinggateway 207.

FIG. 6 depicts the use of extranominal path node 3 as a node forrelaying a packet that leaves sending endpoint 205 to receiving gateway207.

FIG. 7 depicts the use of extranominal, conditioned network 701 as apathway for relaying a packet that leaves sending endpoint 205 forreceiving gateway 207.

FIG. 8 depicts a flowchart of the salient tasks associated with theoperation of the first illustrative embodiment of the present invention.

FIG. 9 depicts a schematic diagram of telecommunications system 900 inaccordance with the second illustrative embodiment of the presentinvention.

FIG. 10 depicts a flowchart of the salient tasks associated with theoperation of the second illustrative embodiment of the presentinvention.

DETAILED DESCRIPTION

The following terms are defined for use in this Specification, includingthe appended claims:

-   -   The term “waveform quality,” and its inflected forms, is defined        as a measure of how well a media signal that is received at a        device compares with what is required to be received at that        device, when assessed at the waveform level. A media signal can        be an audio signal, a video signal, a modem traffic signal, a        TTY signal, a facsimile signal, or some other signal that can be        characterized as having a waveform. The device can be the        intended destination of the media signal within a        telecommunications system or it can be an intermediate node        within the telecommunications system. Waveform quality is        distinguished from quality of service, which was defined        earlier, in that quality of service is a measure that is        performed at the packet level. Waveform quality is a function        of, but is not limited to, one or more of the following waveform        characteristics:        -   i. loudness,        -   ii. audio distortion,        -   iii. noise,        -   iv. fading,        -   v. crosstalk,        -   vi. echo, and        -   vii. video distortion (e.g., spatial, temporal, optical,            etc.).    -   The term “source node,” and its inflected forms, is defined as        the node in a telecommunications system that originates a media        signal, in a particular call or session. The term “destination        node,” and its inflected forms, is defined as the node in a        telecommunications system that is the intended recipient of the        media signal, in the particular call or session.    -   A “communication path,” and its inflected forms, is defined as        the physical route between a source and destination node in a        network. There can be more than one communication path between a        pair of source and destination nodes.    -   The term “sending node,” and its inflected forms, is defined as        the node on the edge of a network that is part of a broader        telecommunications system, where the node sends packets into the        network (e.g., an Internet Protocol network, etc.). The term        “receiving node,” and its inflected forms, is defined as the        node on the edge of the network, where the node receives packets        from the network. Note that, for a given packet session, a        sending node can also be a source node or a receiving node can        also be a destination node, or both.    -   A “network path,” and its inflected forms, is defined as the        physical route between a sending and receiving node in a        network. There can be more than one network path between a pair        of sending and receiving nodes.    -   The term “relay node,” and its inflected forms, is defined as an        intermediate node that receives a packet and forwards at least        part of that packet to the receiving node on the other end of        the IP network. The address of the receiving node is part of the        forwarding instructions that the relay node receives, either        explicitly or implicitly.

This Specification comprises two illustrative embodiments. The firstillustrative embodiment represents the present-invention technique ofswitching between network paths in a packet-switched network that ispart of a first telecommunications system, and is described with respectto FIGS. 2 through 8. The second illustrative embodiment represents thepresent-invention technique of switching between communication pathsthat traverse different combinations of gateways in a secondtelecommunications system, and is described with respect to FIGS. 9 and10. Both techniques use the waveform quality of media that istransmitted in packets along one or more paths, to determine which pathor paths to use for future packet transmissions. As those who areskilled in the art will appreciate, after reading this Specification,the techniques can be used separately or can be combined. For example,the switching between networks paths (e.g., direct path, indirect paths,etc.) of the first illustrative embodiment can be used in combinationwith the switching between gateways of the second illustrativeembodiment.

In accordance with the first illustrative embodiment of the presentinvention, FIG. 2 depicts a schematic diagram of telecommunicationssystem 200. System 200 comprises telephones 201 and 209, Public SwitchedTelephone Network (PSTN) subnetworks 202 and 208, Internet Protocol (IP)gateways 203 and 207, Internet Protocol network 204, and InternetProtocol endpoints 205 and 206, interconnected as shown. System 200enables telephones 201 and 209 and endpoints 205 and 206, as well asother telecommunications terminals, to communicate with each othervarious kinds of media such as audio, video, and so forth.

The first illustrative embodiment is a hybrid telecommunications systemthat comprises portions of the Public Switched Telephone Network and anInternet Protocol-based network. As those who are skilled in the artwill appreciate, after reading this specification, the technique of thepresent invention that is described with respect to FIGS. 2 through 8can be applied to telecommunications systems that comprise othercombinations of networks and of elements within those networks. As afirst example, in some alternative embodiments, an enterprise network(circuit-switched or otherwise) with private branch exchange equipmentcan be present, instead of or in addition to one or both PSTNsubnetworks 202 and 208. As a second example, in some alternativeembodiments, Internet Protocol (IP) network 204 can be the publicInternet or an enterprise IP network, instead of in addition to theservice provider IP network depicted. Furthermore, as those who areskilled in the art will appreciate, the technique of the presentinvention described below can be applied to where nodes other than thosedepicted are present, such as media servers, voice or video messagingsystems, interactive voice response (IVR) systems, and conferencingsystems. The present invention is equally well suited for implementationin telecommunications systems that are private, public, or a combinationof the two, as well as in telecommunications systems that are wireline,wireless, or a combination of the two.

Each of telephones 201 and 209 is an analog telecommunications terminal,as is known in the art, which is capable of making calls to or receivingcalls from any other telecommunications terminal—PSTN-based orIP-based—in telecommunications system 200. In some alternativeembodiments, one or both of telephones 201 and 209 are digital. It willbe clear to those skilled in the art how to make and use telephones 201and 209.

Public Switched Telephone Network subnetworks 202 and 208 are portionsof the Public Switched Telephone Network (PSTN), which is well-known inthe art. Subnetwork 202 comprises access paths, switches, andtransmission paths, in a combination of analog and digital technology,which enable telephone 201 to communicate with other terminals.Subnetwork 208 also comprises access paths, switches, and transmissionpaths, in a combination of analog and digital technology, which enabletelephone 209 to communicate with other terminals. Each depicted portionof the PSTN might comprise wireline equipment, wireless equipment, orboth wireline and wireless equipment.

Internet Protocol gateways 203 and 207 are nodes that act as accesspoints into Internet Protocol network 204 for signals from PSTNsubnetworks 202 and 208, respectively. One or both of gateways 203 and207 perform some or all of the tasks that are described below and withrespect to FIG. 8, with or without the assistance of PSTN subnetworks202 and 208.

Each of Internet Protocol endpoints 205 and 206 is a packet-capabletelecommunications terminal that communicates via the Internet Protocol.Each endpoint is capable of making calls to or receiving calls from anyother telecommunications terminal—PSTN-based or IP-based—intelecommunications system 200. Examples of an IP-based endpoint includea Session-Initiation Protocol (SIP) endpoint, an H.323 endpoint, ageneric IP-based endpoint, and so forth. One or both of endpoints 205and 206 perform some or all of the tasks that are described below andwith respect to FIG. 8.

Internet Protocol network 204 is a packet-switched network that iscapable of transporting packets between edge nodes (i.e., sending nodesand receiving nodes) by using the Internet Protocol, in well-knownfashion. In some embodiments, network 204 is the Internet. Network 204,along with gateways 203 and 207 and endpoints 205 and 206, composes whatis referred to in the specification as subsystem 210. In accordance withthe first illustrative embodiment, the nodes in subsystem 210interoperate by using the Internet Protocol. Nevertheless, it will beclear to those skilled in the art, after reading this disclosure, how toapply the present invention to telecommunications systems and subsystemsthat interoperate using an internetworking protocol other than or inaddition or the Internet Protocol (e.g., asynchronous transfer mode,multiprotocol label switching [MPLS], etc.) and any of a variety ofnetwork or link products (e.g., Ethernet, SONET, frame relay, IEEE802.11, etc.).

FIG. 3 depicts a schematic diagram of the salient components ofsubsystem 210 in accordance with the first illustrative embodiment ofthe present invention. Subsystem 210 comprises gateway 203, endpoint205, endpoint 206, gateway 207, and network 204, interconnected asshown. FIG. 3 also depicts the physical resources that compose network204. As those who are skilled in the art will appreciate, in somealternative embodiments, a different configuration of physical resourcesmight compose network 204.

In accordance with the first illustrative embodiment of the presentinvention, endpoint 205 is depicted as the sending node of trafficpackets (e.g., media packets, control packets, etc.) that aretransported through network 204, and gateway 207 is depicted as thereceiving node of those traffic packets. However, it will be clear tothose skilled in the art, after reading this specification, how to applythe present invention to other combinations of sending and receivingnodes (e.g., gateway 203 and endpoint 206, etc.). Furthermore, althoughnot depicted for clarity purposes, gateways 203 and 207 areinterconnected with PSTN subnetworks 202 and 208, respectively, andexchange signals with those PSTN subnetworks, as shown in FIG. 2.

Network 204 does not provide a waveform quality guarantee for the media(e.g., audio, video, etc.) that is transmitted in any packet or streamof packets such as Real-time Transport Protocol (RTP) packets, as knownin the art, that network 204 transports—for example, from sendingendpoint 205 to receiving gateway 207. Therefore, the provisioning ofreal-time services, such as streaming audio and telephony, from a sourcenode to a destination node in telecommunications system 200, isproblematic without the present invention. In accordance with the firstillustrative embodiment, network 204 does, however, provide aquality-of-service guarantee to one or more packets or streams ofpackets that it transports. Still, in some alternative embodiments, asthose who are skilled in the art will appreciate, network 204 might alsonot provide a quality-of-service guarantee to any packet or stream ofpackets that it transports.

Network 204 is a packet-switched, Internet Protocol-based network thatcomprises a plurality of nodes and their physical interconnections,which are arranged in the topology shown. It will be clear to thoseskilled in the art, however, after reading this specification, how tomake and use alternative embodiments of the present invention withnetworks that comprise any number of nodes and have any topology. Inparticular, it will be clear to those skilled in the art, after readingthis specification, how to make and use embodiments of the presentinvention with a type of packet-switched network other than one that isIP-based.

Each node in network 204 is capable of receiving a packet and offorwarding that packet to another node, in well-known fashion, based onthe address of the receiving node in the packet. For example, when node11 receives a packet from sending endpoint 205, which packet containsnode 26 as its address, node 11 must decide which of its adjacentnodes—nodes 7, 15, and 19—to forward the packet to.

Each node in network 204 decides which adjacent node to give each packetto based on: (1) the address of the receiving node in the packet, and(2) a routing table in the node. Table 1 depicts an example of a routingtable for node 11 in accordance with the first illustrative embodimentof the present invention. Note that the routing table for each node is,in general, different from node to node.

TABLE 1 Routing Table for Node 11 Receiving Preferred First Second NodeNext Alternative Alternative Address Node Next Node Next Node  1  7 1519  2  7 15 19  3  7 15 19 . . . . . . . . . . . . 26 15  7 19 . . . . .. . . . . . . 37 19 15  7 38 19 15  7 39 19 15  7

When all of the resources in the network are functioning normally andthere is little network congestion or other impairments, each nodeforwards a packet to the preferred next node listed in the routingtable. For example, when node 11 receives a packet with the address 26,the preferred next node is node 15. Each node forwards a packet to thenode listed as the entry for the preferred next node and the packetprogresses from one preferred next node to the next and the next and soon until the packet reaches its receiving node. For the purposes of thisspecification, the “primary nominal path” is defined as the chain ofpreferred next nodes from a sending node to a receiving node.

In contrast, when the preferred next node is not functioning normally orthere is congestion at the preferred next node or other knownimpairments, the routing node can alternatively route the packet to thefirst alternative next node. For example, the first alternative nextnode at node 11 for a packet with the address 26 is node 7. And when thefirst alternative node is not functioning or there is congestion at thefirst alternative next node, the routing node can route the packet tothe second alternative next node. The second alternative next node atnode 11 for a packet with the address 26 is node 19.

FIG. 4 depicts the primary nominal path through network 204 from sendingendpoint 205 to receiving gateway 207, which comprises nodes 11, 15, 20,24, 29, 25, 22, and 26. For any pair of sending and receiving nodes,there always exists one primary nominal path.

When any of the nodes in the primary nominal path are not functioning orare experiencing congestion, a node in the primary nominal path candivert the packet from the primary nominal path onto an “alternativenominal path.” For the purposes of this specification, an “alternativenominal path” is defined as a chain of preferred and alternative nextnodes from a sending node to a receiving node.

FIG. 5 depicts the primary nominal path and all of the alternativenominal paths through network 204 from sending endpoint 205 to receivinggateway 207. For the purposes of this specification, a node in a networkthat is within the subgraph of nominal paths is defined as a “nominalpath node” and a node that is not within the subgraph of nominal pathsis defined as an “extranominal path node.”

Network 204, in the prior art and without the advantage of the presentinvention, provides a degree of robustness within the subgraph ofnominal paths with respect to quality of service metrics such asbandwidth, error rate, and latency—but not necessarily with respect towaveform quality metrics such as echo performance, noise performance,loudness performance, and so forth. In contrast, the first illustrativeembodiment uses both nominal and extranominal path nodes to increase thelikelihood that the waveform quality goals for media transmitted in oneor more packets are achieved.

For the purposes of this specification, the term “indirect” path isdefined as a path from a sending node to a receiving node through one ormore specified relay nodes, regardless of whether each relay node is anominal path node or not. Some, but not all, indirect paths are nominalpaths. Conversely, and for the purposes of this specification, the term“direct” path is defined as a path from a sending node to a receivingnode without a specified relay node. All direct paths are nominal paths.

FIG. 6 depicts the use of extranominal path node 3 as a relay node for apacket that leaves sending endpoint 205 for receiving gateway 207. Inthis case, the packet takes a first path that is a nominal path (eitherprimary or alternative) from sending endpoint 205 to node 3; the packetthen takes a second path that is a nominal path (either primary oralternative) from node 3 to receiving gateway 207. The path from sendingendpoint 205 to receiving gateway 207 through node 3 is indirect—incontrast to one of the direct, nominal paths from sending endpoint 205to receiving gateway 207—because sending endpoint 205 specifies node 3in the packet's path. In other words, when sending endpoint 205specifies at least one relay node in the packet's path on its way toreceiving gateway 207, the packet is taking an indirect path.

In accordance with the first illustrative embodiment of the presentinvention, extranominal path node 3 serves as the sole relay node for apacket that leaves sending endpoint 205 for receiving gateway 207. Itwill be clear, however, to those skilled in the art that the indirectpacket transmission method of the first illustrative embodiment can usemultiple relay nodes and, therefore, multiple indirections to transmitpackets from the sending to receiving node. A collection of relay nodescan be logically interconnected in some topology and can use rules orpolicies, or both, for selecting logical interconnections. The resultinglogical network is often referred to as an “overlay network” or“application-level network.”

FIG. 7 depicts the use of extranominal, alternative network 701 as apathway for relaying a packet that leaves sending endpoint 205 toreceiving gateway 207. In accordance with the first illustrativeembodiment, network 701 is conditioned to have waveform characteristicsthat are similar to or better than those of network 204. In someembodiments, network 701 comprises a portion of the Public SwitchedTelephone Network, one or more private networks, another IP network, ora network that operates in accordance with another protocol (e.g., ATM,frame relay, etc.). Network 701 is interconnected with other nodes ofsubsystem 210 as shown. In accordance with the first illustrativeembodiment, network 701 is conditioned to provide a guaranteed, waveformquality of media that it transports. For example, network 701 cantransport the media in packets from sending endpoint 205 to receivinggateway 207 with a waveform quality guarantee. A sending node such assending endpoint 205 might select network 701 to transport at least somepackets for applications that require the media in those packets to bereceived by the receiving node at a minimum waveform quality level orbetter. One example of a minimum waveform quality level is in audiotelephony, in which the parties involved in a call will typicallytolerate the presence of echo only up to, but not exceeding, a maximumdelay such as 100 milliseconds. It will be clear to those skilled in theart how to make and use network 701 to provide a waveform qualityguarantee.

FIGS. 6 and 7 depict scenarios in which sending endpoint 205 hasspecified a relay node within network 204 or a pathway that is externalto network 204, such as through network 701. As those who are skilled inthe art will appreciate, after reading this specification, changing thetransmission path for a call or session, such as from a direct path toan indirect path, purely based on quality of service does notnecessarily provide an improvement in waveform quality. For example,achieving a satisfactory packet delay between sending endpoint 205 andreceiving gateway 207 might not necessarily result in a satisfactoryecho characteristic for a call that involves the user of endpoint 205and the user of telephone 209.

FIG. 8 depicts a flowchart of the salient tasks associated with theoperation of the first illustrative embodiment of the present invention.In accordance with the first illustrative embodiment, telecommunicationsendpoint 205 evaluates the waveform quality of media that is transmittedalong one or more network paths. As those who are skilled in the artwill appreciate, in some alternative embodiments, a physically differentnode or another type of node, other than IP-based endpoint 205, eitherwithin or external to network 204, can perform some or all of the tasksthat are described below.

As an example, FIG. 8 illustrates the transfer of packets from sendingendpoint 205 to receiving gateway 207, where sending endpoint 205 isalso the source node of the session and telephone 209 is the destinationnode of the session. Endpoint 205 and gateway 207 are used forillustrative purposes; however, it will be clear to those who areskilled in the art how to apply the present invention to thetransmission of media between sending and receiving nodes different fromthose described in the example, and between source and destination nodesdifferent from those described.

At task 801, sending endpoint 205 transmits a first packet to receivinggateway 207 through a direct path in well-known fashion.

At task 802, sending endpoint 205 evaluates the waveform quality ofmedia that is transmitted along a direct path from sending endpoint 205to receiving gateway 207. In evaluating the waveform quality, endpoint205 compares one or more measurements that it receives against apre-determined requirement. As is well known to those skilled in theart, the waveform quality that is associated with the direct path ismeasured by:

-   -   i. the loudness or intensity of the waveform,    -   ii. the audio distortion that is present in the waveform,    -   iii. the noise that is present in the waveform,    -   iv. the fading that has occurred in the waveform,    -   v. the crosstalk that is present in the waveform,    -   vi. the echo that that is present in the waveform,    -   vii. the video distortion that is present in the waveform (e.g.,        spatial, temporal, optical, etc.)    -   viii. a derivative or associated function of one or more of i        through vii, or    -   ix. any combination of i through viii.

For example, sending endpoint 205 can evaluate the waveform qualityassociated with the direct path by transmitting, to receiving gateway207, a test packet that comprises either an explicit or implicitinstruction for gateway 207 to return one or more measurements toendpoint 205. Upon receiving the instruction, gateway 207 eithermeasures internally or obtains an external measurement of the waveformof the media signal that is conveyed in one or more traffic packetsreceived from sending endpoint 205. The measurement of a waveform can betaken at or in the proximity of gateway 207 or elsewhere intelecommunications system 200 (e.g., in PSTN subnetwork 208, in IPnetwork 204, etc.). The measurement can be taken in the transmittedpath—for example, to measure the loudness of the media signal—or can betaken in the return path—for example, to measure the echo from the mediasignal. Gateway 207 can perform this task alone or with one or moreelements in PSTN subnetwork 208 to obtain one or more measurements ofthe waveform. Alternatively, another type of node other than a gatewaycan obtain the measurement on behalf of sending endpoint 205 orwhichever node the evaluating node is. As those who are skilled in theart will appreciate, other techniques that are known in the art, such asPSTN-centric techniques, can be applied to measure the waveform qualityof media that is transmitted along a direct path.

Furthermore, as those who are skilled in the art will appreciate, insome alternative embodiments, a node other than sending endpoint 205 canevaluate the waveform quality, such as receiving gateway 207—in whichcase, the evaluating node can return the results of the evaluation toendpoint 205, instead of or in addition to returning a measurement.

At task 803, sending endpoint 205 evaluates the waveform quality ofmedia that is transmitted along a first indirect network path fromsending endpoint 205 to receiving gateway 207 through node 3. In thiscase, node 3 is an extranominal node, but it will be clear to thoseskilled in the art how to make and use alternative embodiments of thepresent invention in which node 3 is a nominal path node.

Various techniques can be used to evaluate the waveform quality of acandidate path (e.g., through node 3, etc.), in which one or moremeasurements are compared against either a pre-determined requirement oragainst measurements associated with the path currently in use. As thosewho are skilled in the art will appreciate, other techniques than thosedescribed can be used to evaluate the waveform quality of media that istransmitted along a candidate path.

In a first illustrative technique, endpoint 205 can acquire savedmeasurements of waveforms of media that has been transmitted previouslythrough endpoint 205, node 3, and gateway 207 to the same destinationnode (e.g., telephone 209, etc.).

In a second illustrative technique, endpoint 205 transmits a testwaveform to a node in PSTN subnetwork 208 by encoding the waveform intoa stream of test packets that are sent to node 3. The test packetsfurther comprise an instruction for node 3 to forward the packets toreceiving gateway 207 (and to forward the test waveform to PSTNsubnetwork 208) with an instruction for receiving gateway 207. Theinstruction for gateway 207 is to return one or more measurements of thetest waveform to sending endpoint 205, as measured either at gateway 207or elsewhere such as in PSTN subnetwork 208. Gateway 207 can measure thewaveform quality that is associated with a network path by applyingvarious techniques that are known in the art, such as PSTN-centrictechniques.

In a third illustrative technique, endpoint 205 temporarily routes theactual traffic packets of the media session through node 3, for thepurpose of obtaining a measurement of the waveform quality. The trafficpackets further comprise an instruction for node 3 to forward thepackets to receiving gateway 207 with an instruction for receivinggateway 207, which instructs gateway 207 to return one or moremeasurements of the waveform to sending endpoint 205, as measured eitherat gateway 207 or elsewhere such as in PSTN subnetwork 208.

At task 804, when the waveform quality that is associated with the firstindirect network path is more advantageous than that associated with thedirect path, sending endpoint 205 transmits a second packet to node 3,wherein node 3 is explicitly instructed to forward the second packet toreceiving gateway 207. It is well known to those skilled in the art howto instruct node 3 to forward the packet to receiving gateway 207. Forexample, the packet could itself carry a re-direct instruction asmentioned earlier or, as an alternative, sending endpoint 205 couldtransmit a signaling packet to node 3 to direct it to forward packetsfrom endpoint 205 to receiving gateway 207.

In some alternative embodiments, sending endpoint 205 determines whetherthe waveform quality that is associated with the direct path issatisfactory—that is, exceeds pre-determined requirements withoutaccounting for the quality associated with other network paths—orunsatisfactory. This is in contrast to comparing the waveform qualityassociated with the first indirect path against the waveform qualitythat is associated with the direct path. In those embodiments, theevaluating of the waveform quality associated with the first indirectpath can be skipped, and if the waveform quality is unsatisfactory,sending endpoint 205 transmits the second packet via the first indirectpath through node 3.

At task 805, sending endpoint 205 evaluates the waveform quality ofmedia that is transmitted along a second indirect path from sendingendpoint 205 to receiving gateway 207 through yet another node such asnode 32, for example. In this example, node 32 is a nominal path node,but it will be clear to those skilled in the art, after reading thisspecification, how to make and use alternative embodiments of thepresent invention in which the node in the evaluation is an extranominalpath node. Sending endpoint 205 can evaluate the waveform qualityassociated with the path from sending endpoint 205 to receiving gateway207 through node 32 in the same or a different manner from thatdescribed at task 803.

At task 806, when the waveform quality that is associated with thesecond indirect path (through node 32) is more advantageous than thewaveform quality associated with the first indirect path (through node3) or the direct path, sending endpoint 205 transmits a third packetfrom sending endpoint 205 to node 32, wherein node 32 is explicitlyinstructed to forward the second packet to receiving gateway 207. It iswell known to those skilled in the art how to instruct node 32 toforward the packet to receiving gateway 207.

At task 807, sending endpoint 205 re-evaluates the waveform quality ofmedia that is transmitted along a path from sending endpoint 205 toreceiving gateway 207 through the direct path. Sending endpoint 205 canre-evaluate the waveform quality associated with the direct path in asimilar manner or a different manner from how it evaluates the waveformat task 802 or 803.

At task 808, when the waveform quality that is associated with thedirect network path is more advantageous than that of either the firstor second indirect paths, sending endpoint 205 transmits a fourth packetfrom sending endpoint 205 to receiving gateway 207 through the directpath.

In some alternative embodiments, sending endpoint 205 determines whetherthe waveform quality that is associated with the direct path issatisfactory or unsatisfactory, instead of comparing the waveformquality associated with the first or second indirect paths with thewaveform quality that is associated with the direct path. In thoseembodiments, if the waveform quality associated with the direct path issatisfactory, sending endpoint 205 transmits the fourth packet via thedirect path.

In accordance with the second illustrative embodiment of the presentinvention, FIG. 9 depicts a schematic diagram of telecommunicationssystem 900. System 900 comprises, interconnected as shown: InternetProtocol (IP) endpoints 901 and 911; IP networks 902 and 910; gateways903, 904, 908, and 909; Public Switched Telephone Network 905; andtelephones 906 and 907. System 900 enables IP endpoints 901 and 909 andtelephones 906 and 907, as well as other telecommunications terminals,to communicate with each other various kinds of media such as audio,video, and so forth. A relevant property of system 900 is that any twocommunication instances between the same pair of IP endpoints ortelephones can traverse different gateways. For example, in oneinstance, the media flow between IP endpoints 901 and 911 might traversegateways 903 and 908; in another instance, the media flow between IPendpoints 901 and 911 might traverse gateways 904 and 909. Note thattelecommunications system 900 does not provide a waveform qualityguarantee for the media (e.g., audio, video, etc.) that is transmittedalong at least some communication paths.

The second illustrative embodiment is a hybrid telecommunications systemthat comprises the Public Switched Telephone Network and multipleInternet Protocol-based networks. As those who are skilled in the artwill appreciate, after reading this specification, the technique of thepresent invention that is described with respect to FIGS. 9 and 10 canbe applied to telecommunications systems that comprise othercombinations of networks and of elements within those networks. As afirst example, in some alternative embodiments, an enterprise network(circuit-switched or otherwise) with private branch exchange equipmentcan be present, instead of or in addition to Public Switched TelephoneNetwork 905. As a second example, in some alternative embodiments, oneor both of Internet Protocol (IP) networks 902 and 910 can be the publicInternet or enterprise IP networks, instead of in addition to theservice provider IP networks depicted. Furthermore, as those who areskilled in the art will appreciate, the technique of the presentinvention described below can be applied to where nodes other than thosedepicted are present, such as media servers, voice or video messagingsystems, interactive voice response (IVR) systems, and conferencingsystems. The present invention is equally well suited for implementationin telecommunications systems that are private, public, or a combinationof the two, as well as in telecommunications systems that are wireline,wireless, or a combination of the two.

Each of Internet Protocol endpoints 901 and 911 is a packet-capabletelecommunications terminal that communicates via the Internet Protocol.Each endpoint is capable of making calls to or receiving calls from anyother telecommunications terminal—PSTN-based or IP-based—intelecommunications system 900. Examples of an IP-based endpoint includea Session-Initiation Protocol (SIP) endpoint, an H.323 endpoint, ageneric IP-based endpoint, and so forth. One or both of endpoints 901and 911 perform some or all of the tasks that are described below andwith respect to FIG. 10.

Each of Internet Protocol networks 902 and 910 is a packet-switchednetwork that is capable of transporting packets between edge nodes(i.e., sending nodes and receiving nodes) by using the InternetProtocol, in well-known fashion. In some embodiments, one or both ofnetworks 902 and 910 is the Internet. Each of networks 902 and 910 cancomprise wireline equipment, wireless equipment, or both wireline andwireless equipment.

In accordance with the second illustrative embodiment, the nodes thatconstitute each of networks 902 and 910 interoperate by using theInternet Protocol. However, it will be clear to those skilled in theart, after reading this disclosure, how to apply the present inventionto telecommunications systems and subsystems that interoperate using aninternetworking protocol other than or in addition or the InternetProtocol (e.g., asynchronous transfer mode, multiprotocol labelswitching [MPLS], etc.) and any of a variety of network or link products(e.g., Ethernet, SONET, frame relay, IEEE 802.11, etc.).

Internet Protocol gateways 903 and 904 are nodes that act as accesspoints into Internet Protocol network 902 for signals from PSTN 905 and,as such, are contiguous with network 902, but are non-contiguous withnetwork 910. Gateways 908 and 909 act as access points into network 910for signals from PSTN 905 and, as such, are contiguous with network 910,but are non contiguous with network 902.

Public Switched Telephone Network 905, as is well-known in the art,comprises access paths, switches, and transmission paths, in acombination of analog and digital technology, which enable telephones906 and 907 to communicate with other terminals. Telephones 906 and 907are telecommunications terminals that are capable of making calls to orreceiving calls from any other terminal in system 900. PSTN 905 cancomprise wireline equipment, wireless equipment, or both wireline andwireless equipment.

FIG. 10 depicts a flowchart of the salient tasks associated with theoperation of the second illustrative embodiment of the presentinvention. In accordance with the second illustrative embodiment,telecommunications endpoint 901 evaluates the waveform quality of mediathat is transmitted along one or more communication paths. As those whoare skilled in the art will appreciate, in some alternative embodiments,a physically different node or another type of node, other than IP-basedendpoint 901, either within or external to network 902, can perform someor all of the tasks that are described below.

As an example, FIG. 10 illustrates the transfer of packets from sourceendpoint 901 to destination endpoint 911 along one or more communicationpaths that traverse network 902. Endpoints 901 and 911 are used forillustrative purposes; however, it will be clear to those who areskilled in the art how to apply the present invention to thetransmission of media between source and destination nodes differentfrom those described in the example. In addition to traversing network902, the communication paths traverse gateways x and y, where gateway xis gateway 903 or gateway 904 as depicted, and gateway y is gateway 908or gateway 909 as depicted. It will also be clear to those skilled inthe art how to apply the present invention when the number of gateways,and therefore the paths between them, is different from that used in theexample.

At task 1001, source endpoint 901 transmits a first packet todestination endpoint 911 through a first communication path inwell-known fashion. In the example, the first communication pathtraverses network 902, gateway 903, and gateway 908.

At task 1002, source endpoint 901 evaluates the waveform quality ofmedia that is transmitted along the first communication path. Inevaluating the waveform quality, endpoint 901 compares one or moremeasurements that it receives against a pre-determined requirement. Asis well known to those skilled in the art, the waveform quality that isassociated with the first communication path is measured by:

-   -   i. the loudness or intensity of the waveform,    -   ii. the audio distortion that is present in the waveform,    -   iii. the noise that is present in the waveform,    -   iv. the fading that has occurred in the waveform,    -   v. the crosstalk that is present in the waveform,    -   vi. the echo that that is present in the waveform,    -   vii. the video distortion that is present in the waveform (e.g.,        spatial, temporal, optical, etc.)    -   viii. a derivative or associated function of one or more of i        through vii, or    -   ix. any combination of i through viii.        Sending endpoint 901 evaluates the waveform quality of media in        this second illustrative embodiment similarly to how endpoint        205 evaluates the waveform quality in the first illustrative        embodiment, as described above and with respect to task 802.

As those who are skilled in the art will appreciate, in some alternativeembodiments a node other than source endpoint 901 can evaluate thewaveform quality, such as destination endpoint 911—in which case, theevaluating node can return the results of the evaluation to endpoint901, instead of or in addition to returning a measurement.

At task 1003, source endpoint 901 evaluates the waveform quality ofmedia that is transmitted along a second communication path from sourceendpoint 901 to destination endpoint 911. In the example, the secondcommunication path traverses network 902, gateway 904, and gateway 908.In some embodiments, endpoint 901 also evaluates the waveform quality ofmedia that is transmitted along other communication paths (e.g., throughgateways 904 and 909, through gateways 903 and 909, etc.).

Various techniques can be used to evaluate the waveform quality of acandidate path (e.g., through gateway 904, through gateway 909, etc.),in which one or more measurements are compared against either apre-determined requirement or against measurements associated with thepath currently in use. As those who are skilled in the art willappreciate, other techniques than those described can be used toevaluate the waveform quality of media that is transmitted along acandidate path. Some illustrative techniques are described above andwith respect to task 803; those who are skilled in the art willappreciate, after reading this specification, how to apply thosetechniques here.

At task 1004, when the waveform quality that is associated with thesecond communication path, or with some other evaluated path, is moreadvantageous than that associated with the first communication path,source endpoint 901 transmits a second packet to endpoint 911 along thepath with the more advantageous waveform quality. For example, if thesecond communication path is selected, source endpoint 901 transmits thepacket to gateway 904, gateway 904 transmits the media informationcontained in the packet along a path to gateway 908, and gateway 908re-packetizes the media information and transmits the packet to endpoint911, in well-known fashion.

In some alternative embodiments, source endpoint 901 determines whetherthe waveform quality that is associated with the first communicationpath is satisfactory—that is, exceeds pre-determined requirementswithout accounting for the quality associated with other communicationpaths—or unsatisfactory. This is in contrast to comparing the waveformquality associated with other communication paths against the waveformquality that is associated with the first communication path. In thoseembodiments, the evaluating of the waveform quality associated with thesecond communication path can be skipped, and if the waveform quality isunsatisfactory, source endpoint 901 transmits the second packet via thesecond communication path.

At task 1005, sending endpoint 205 evaluates the waveform quality ofmedia that is transmitted along a third communication path from sourceendpoint 901 to destination node 911. In the example, the thirdcommunication path traverses network 902, gateway 904, and gateway 909.In some embodiments, endpoint 901 also evaluates the waveform quality ofmedia that is transmitted along other communication paths (e.g., throughgateways 903 and 908, through gateways 903 and 909, etc.). Sourceendpoint 901 can evaluate the waveform quality associated with the thirdcommunication path in the same or a different manner from that describedat task 1003.

At task 1006, when the waveform quality that is associated with thethird communication path is more advantageous than the waveform qualityassociated with the second communication path (or other evaluatedcommunication paths), source endpoint 901 transmits a third packet todestination endpoint 911 along the third communication path.

At task 1007, source endpoint 901 re-evaluates the waveform quality ofmedia that is transmitted along the first communication path. Endpoint901 can re-evaluate the waveform quality associated with the firstcommunication path in a similar manner or a different manner from how itevaluates the waveform at task 1002 or 1003.

At task 1008, when the waveform quality that is associated with thefirst communication path is more advantageous than that of the second orthird communication path, source endpoint 901 transmits a fourth packetto destination endpoint 911 along the first communication path.

The examples described with respect to FIGS. 8 and 10 change theutilized path in response to evaluating the waveform quality of thetransmitted signals. However, it will be clear to those skilled in theart, after reading this specification, how to affect other call-relatedresources or characteristics in response to the evaluated waveformquality. For example, the techniques of the illustrative embodiments canbe applied to controlling echo that is transmitted in a return path of acall by selectively disabling or re-enabling the flow of packets throughthe packet-switched network, in order to mute or unmute, respectively,the signals that contain the echo.

It is to be understood that the above-described embodiments are merelyillustrative of the present invention and that many variations of theabove-described embodiments can be devised by those skilled in the artwithout departing from the scope of the invention. For example, in thisspecification, numerous specific details are provided in order toprovide a thorough description and understanding of the illustrativeembodiments of the present invention. Those skilled in the art willrecognize, however, that the invention can be practiced without one ormore of those details, or with other methods, materials, components,etc.

Furthermore, in some instances, well-known structures, materials, oroperations are not shown or described in detail to avoid obscuringaspects of the illustrative embodiments. It is understood that thevarious embodiments shown in the Figures are illustrative, and are notnecessarily drawn to scale. Reference throughout the specification to“one embodiment” or “an embodiment” or “some embodiments” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment(s) is included in at least one embodimentof the present invention, but not necessarily all embodiments.Consequently, the appearances of the phrase “in one embodiment,” “in anembodiment,” or “in some embodiments” in various places throughout thespecification are not necessarily all referring to the same embodiment.Furthermore, the particular features, structures, materials, orcharacteristics can be combined in any suitable manner in one or moreembodiments. It is therefore intended that such variations be includedwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A method comprising: evaluating, by a firstendpoint, the waveform quality of a media signal that is transmitted bythe first endpoint along a first communication path from a first node toa second node, wherein the first communication path traverses: (i) afirst network that is packet-switched, (ii) a first gateway that iscontiguous with the first network, and (iii) a second gateway that isnon-contiguous with the first network; when the waveform quality isdetermined to be unsatisfactory regardless of a quality-of-service ofthe first communication path, transmitting, by the first endpoint afirst packet along a second communication path from the first node tothe second node, wherein the second communication path traverses thefirst network and at least one of: (i) a third gateway that iscontiguous with the first network, and (ii) a fourth gateway that isnon-contiguous with the first network; wherein the first communicationpath fails to provide a quality-of-service guarantee; wherein theevaluating comprises (i) receiving from the first gateway a measurementof the waveform quality of the media signal, and (ii) comparing themeasurement to a predetermined requirement to determine whether thewaveform quality is satisfactory or unsatisfactory; evaluating thewaveform quality of media that is transmitted along a thirdcommunication path from the first node to the second node, wherein thethird communication path traverses the first network and at least one ofthe third gateway and the fourth gateway; when the waveform quality ofmedia transmitted along the third communication path is moreadvantageous than the waveform quality of media transmitted along thesecond communication path, transmitting a second packet along the thirdcommunication path from the first node to the second node; wherein thethird communication path fails to provide a quality-of-serviceguarantee; re-evaluating the waveform quality of media that istransmitted along the first communication path from the first node tothe second node; and when the waveform quality of media transmittedalong the first communication path is satisfactory, transmitting a thirdpacket along the first communication path from the first node to thesecond node.
 2. The method of claim 1 wherein the first gateway and thesecond gateway are contiguous with a second network, and wherein thecommunication protocols of the first network and the second network aredifferent.
 3. The method of claim 2 wherein the second network is thePublic Switched Telephone Network.
 4. The method of claim 2 wherein thefirst network is Internet Protocol-based.
 5. The method of claim 1wherein the evaluating is based on the quality of service of the firstcommunication path being satisfactory.
 6. The method of claim 1 whereinthe evaluating of the waveform quality of the media signal that istransmitted along the first communication path is performed with respectto one or more of echo, noise, loudness, and audio distortion.
 7. Themethod of claim 1 wherein the evaluating of the waveform quality of themedia signal that is transmitted along the first communication path isperformed with respect to one or more of fading, crosstalk, and videodistortion.
 8. A method comprising: transmitting by a first endpoint afirst packet along a first communication path from the first node to thesecond node, wherein the first communication path traverses: (i) a firstnetwork that is packet-switched, (ii) a first gateway that is contiguouswith the first network, and (iii) a second gateway that isnon-contiguous with the first network; evaluating the waveform qualityof a media signal that is transmitted by the first endpoint along thefirst communication path; evaluating the waveform quality of the mediasignal that is transmitted by the first endpoint along a secondcommunication path from the first node to the second node, wherein thesecond communication path traverses the first network and at least oneof: (i) a third gateway that is contiguous with the first network, and(ii) a fourth gateway that is non-contiguous with the first network;when the waveform quality of the media signal that is transmitted alongthe second communication path is more advantageous than the waveformquality of the media that is transmitted along the first communicationpath, transmitting a second packet along the second communication pathfrom the first node to the second node; wherein the second communicationpath fails to provide a quality-of-service guarantee; wherein (i) theevaluating associated with the first communication path and (ii) theevaluating associated with the second communication path are both basedon the quality-of-service of the first communication path beingsatisfactory; evaluating the waveform quality of media that istransmitted along a third communication path from the first node to thesecond node, wherein the third communication path traverses the firstnetwork and at least one of the third gateway and the fourth gateway;when the waveform quality of media transmitted along the thirdcommunication path is more advantageous than the waveform quality ofmedia transmitted along the second communication path, transmitting athird packet along the third communication path from the first node tothe second node; wherein the third communication path fails to provide aquality-of-service guarantee; re-evaluating the waveform quality ofmedia that is transmitted along the first communication path from thefirst node to the second node; and when the waveform quality of mediatransmitted along the first communication path is satisfactory,transmitting a fourth packet along the first communication path from thefirst node to the second node.
 9. The method of claim 8 wherein thefirst gateway and the second gateway are contiguous with a secondnetwork, wherein the communication protocols of the first network andthe second network are different.
 10. The method of claim 9 wherein thesecond network is the Public Switched Telephone Network.
 11. The methodof claim 9 wherein the first network is Internet Protocol-based.
 12. Themethod of claim 8 wherein the evaluating of the waveform quality ofmedia that is transmitted along the first communication path isperformed with respect to one or more of echo, noise, loudness, andaudio distortion.
 13. The method of claim 8 wherein the evaluating ofthe waveform quality of media that is transmitted along the firstcommunication path is performed with respect to one or more of fading,crosstalk, and video distortion.
 14. A method comprising: transmitting,by a first endpoint, a first packet along a first communication pathfrom a first node to a second node, wherein the first communication pathtraverses: (i) a first network that is packet-switched, (ii) a firstgateway that is contiguous with the first network, and (iii) a secondgateway that is non-contiguous with the first network; evaluating thewaveform quality of a media signal that is transmitted along the firstcommunication path, along a second communication path from the firstnode to the second node, and along a third communication path from thefirst node to the second node, wherein the second communication path andthe third communication path are different, and wherein each of thesecond communication path and the third communication path traverses thefirst network and at least one of: (i) a third gateway that iscontiguous with the first network, and (ii) a fourth gateway that isnon-contiguous with the first network; when the waveform quality of themedia signal that is transmitted along the second communication path isdetermined to be more advantageous than both (i) the waveform quality ofthe media signal that is transmitted along first communication path and(ii) the waveform quality of the media signal that is transmitted alongthe third communication path, transmitting a second packet along thesecond communication path from the first node to the second node;wherein the second communication path fails to provide aquality-of-service guarantee; wherein the determination of whether thewaveform quality of the media signal along the second communication pathis more advantageous is based on a quality-of-service of the secondcommunication path being satisfactory; when the waveform quality ofmedia transmitted along the third communication path is moreadvantageous than the waveform quality of media transmitted along thesecond communication path, transmitting a third packet along the thirdcommunication path from the first node to the second node; wherein thethird communication path fails to provide a quality-of-serviceguarantee; re-evaluating the waveform quality of media that istransmitted along the first communication path from the first node tothe second node; and when the waveform quality of media transmittedalong the first communication path is satisfactory, transmitting afourth packet along the first communication path from the first node tothe second node.
 15. The method of claim 14 wherein the first gatewayand the second gateway are contiguous with a second network, wherein thecommunication protocols of the first network and the second network aredifferent.
 16. The method of claim 15 wherein the second network is thePublic Switched Telephone Network.
 17. The method of claim 15 whereinthe first network is Internet Protocol-based.
 18. The method of claim 14wherein the evaluating of the waveform quality of media that istransmitted along the first communication path is performed with respectto one or more of echo, noise, loudness, and audio distortion.
 19. Themethod of claim 14 wherein the evaluating of the waveform quality ofmedia that is transmitted along the first communication path isperformed with respect to one or more of fading, crosstalk, and videodistortion.